170,725 research outputs found
The experience of baccalaureate international exange nursing students: a phenomenology study
No full textMagnitude modelling of HRTF using principal component analysis applied to complex values
No full textFil: Ramos, Oscar Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigación y Transferencia en Acústica; Argentina.Fil: Ramos, Oscar Alberto. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación y Transferencia en Acústica; Argentina.Fil: Ramos, Oscar Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Tommasini, Fabián Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigación y Transferencia en Acústica; Argentina.Fil: Tommasini, Fabián Carlos. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación y Transferencia en Acústica; Argentina.Fil: Tommasini, Fabián Carlos. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.Fil: Tommasini, Fabián Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Principal components analysis (PCA) is frequently used for modelling the magnitude of the head related transfer functions (HRTFs). Assuming that the HRTFs are minimum phase systems, the phase is obtained from the Hilbert transform of the log-magnitude. In recent years, the PCA applied to HRTFs is also used to model individual HRTFs relating the PCA weights with anthropometric measurements of the head, torso and pinnae. The HRTF log-magnitude is the most used format of input data to the PCA, but it has been shown that if the input data is HRTF linear magnitude, the cumulative variance converges faster, and the mean square error (MSE) is smaller. This study demonstrates that PCA applied directly on HRTF complex values is even better than the two formats mentioned above, that is, the MSE is the smallest and the cumulative variance converges faster after the 8th principal component. Different objective experiments around all the median plane put in evidence the differences which, although small, seem to be perceptually detectable. To elucidate this point, psychoacoustic discrimination tests are done between measured and reconstructed HRTFs from the three types of input data mentioned, in the median plane between −45◦ and +90◦.http://acoustics.ippt.pan.pl/index.php/aa/article/view/294publishedVersionFil: Ramos, Oscar Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigación y Transferencia en Acústica; Argentina.Fil: Ramos, Oscar Alberto. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación y Transferencia en Acústica; Argentina.Fil: Ramos, Oscar Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Fil: Tommasini, Fabián Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigación y Transferencia en Acústica; Argentina.Fil: Tommasini, Fabián Carlos. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación y Transferencia en Acústica; Argentina.Fil: Tommasini, Fabián Carlos. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.Fil: Tommasini, Fabián Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina.Otras Ingenierías y Tecnología
Classificazione dei luoghi con pericolo di esplosione per la presenza di polveri combustibili
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Comparison of simple tests for the non-invasive diagnosis of clinically silent cirrhosis in chronic hepatitis C
No full textBackground: Biopsy is the gold standard for assessing cirrhosis in patients with chronic hepatitis C virus infection, but it is expensive and at risk of complications. Alternative non-invasive methods have been developed but their usefulness remains uncertain. Aim: To compare the accuracy of five non-invasive scores in detecting cirrhosis. Methods: We reviewed the charts and liver biopsies of 228 consecutive, treatment-naïve, hepatitis C virus-positive patients, 13.2% of whom with histological diagnosis of cirrhosis. The five alternative scores were age-platelet index, cirrhosis discriminant score, aspartate transaminases to platelet ratio index, Pohl's index, and aspartate transaminases/alanine transaminases ratio. Results: The specificities of the scores were good (87-100%), but not so their sensitivities (17-67%). Accordingly positive likelihood ratios were generally good but negative likelihood ratios were suboptimal. Combinations of the scores independently related to cirrhosis only slightly change this diagnostic accuracy. Using double cut-offs to exclude/diagnoses cirrhosis, cirrhosis discriminant score classified 21% of patients without misdiagnoses and aspartate transaminases to platelet ratio index classified 85% of case with 9% of misdiagnoses. Conclusions: The five scores showed variable sensitivities and specificities in detecting liver cirrhosis, both individually and in combination. The use of double cut-off points may make the cirrhosis discriminant score and aspartate transaminases to platelet ratio index useful to reduce the number of patients submitted to liver biopsy
Analysis of wind-wave induced erosion in the Venice Lagoon in the last four centuries: field observations and modelling
No full textTidal systems are subjected to a variety of internal and external drivers whose interplay and feedbacks affect the shape and the morphological evolution of typical tidal landforms such as channel networks, salt marshes and tidal flats. Several studies have been carried out describing the various processes that drive the evolution of tidal landforms (e.g., the hydrodynamic circulation, the consequences of tidal currents and wind waves on sediment dynamics, vertical and horizontal dynamics of salt marshes, sea level rise and human interferences). Understanding the positive feedbacks existing between salt-marsh erosion, tidal-flat widening and deepening and more energetic wave generation by means of observational evidence and numerical models is a critical step to predict the response of tidal landforms to future environmental changes. With this aim we first improved current our knowledge on the ancient configurations of the Venice lagoon through the bathymetric reconstruction of the oldest map, dating back to 1611, providing a realistic representation of its morphological features. This furthermore allowed us to gain new insights on the hydrodynamic changes occurred in the last four centuries. We then compared different existing model approaches, in order to unravel the implications of different assumptions and formulations used to model wave dynamics in shallow tidal basins. Subsequently, we analysed the effects of wave action on marsh boundaries and how the wave field has changed in the last four centuries with the aim of further emphasizing the feedbacks existing between the overall erosion of the Venice Lagoon and the increase in wave power density. Finally, we analysed the bottom shear stress distribution obtained for different configurations of the Venice Lagoon, in order to support the possibility of describing wind-wave induced bottom erosion as a marked Poisson process.
The main results from this work highlighted that: I) the most important mophodynamic changes in the Venice Lagoon have started in the last century and were mainly triggered by human interferences; II) the assumptions adopted in different modelling framework strongly influence the computation of the bottom shear stress induced by waves, in particular when very shallow water depths are considered; III) the salt-marsh erosion rate is linearly related to the mean wave power density; IV) the erosive trend of the Venice Lagoon during the last four centuries can be explained also by the increase in wave power density and by the analysis of bottom shear stress distribution; V) wind-wave induced erosion processes over tidal flats can be described as marked Poisson processes for all the past and current lagoon configurations, thus leading important consequences for the prediction of future scenarios and implications for the long-term morphodynamic modelling of tidal environments
Virtual instrument superheterodyne wave analyzer for teaching purposes
No full textPraga, Repubblica Cec
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